Singing Tesla coils

The video above is ArcAttack! playing the classic “Popcorn” through their signature Tesla coils. Solid state Tesla coils (SSTC) can generate sound using what [Ed Ward] calls pulse repetition frequency (PRF) modulation. The heat generated by the plasma flame causes rapid expansion of the surrounding air and a resulting soundwave. An SSTC can be operated at just about any frequency, so you just need to build a controller to handle it. The task is made more difficult because very few electronics are stable in such an intense EM field. [Ed] constructed a small Faraday cage for his microcontroller and used optical interconnects to deliver the signals to the Tesla coils.

This was at a regional Burning Man event called Flipside. Very cool to watch and listen to. Really impressive control schemes on the musical components. Ididnt get a chance to look at it during the day all the gear was put away. Was talking to the guy who thought it up. 3 Octaves worth of notes so far. They were experiment with jacobs ladders and other devices for different tunes. Absolutely brilliant

Quick question: I always only see coils playing single notes songs. Is there a real limitation that prevents playing full wave sound, or would it require that it’s at least converted to a PMS signal first ?

These coils are DRSSTCs – double-resonant solid-state Tesla coils. They are powered with IGBTs, which limits the frequency to less than 20 kHz at best.

The reason for this is because they pass so much current – he wants those sparks as big as possible. These were 5 ft last I heard and they’re not even turned up all the way because they’re afraid to blow them before show season is up!

MOSFETs switch at a higher frequency but also have a much higher resistance. You can build a full-wave coil but your power is limited by what the MOSFETs can handle. If it is analog modulated there is A LOT of heat dropped, so even though the IGBT may be able to modulate at audio it should only be switched for heat concerns. If MOSFETs are pulse-width modulated like a class D amplifier it’s not so bad but still nowhere close to 5 ft without massive MOSFET bricks.

The two links at the top of Steve Ward’s site (the fella from Illinois) give a lot of info about the hows and whys with schematics.

you can get tesla coils that pretty much replace a speaker and have very good fidelity but the spark is about 1 – 2 inches and they don’t really “match” the sound. look up Audio SSTCs from eastern voltage research.